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A single gene controls a key difference between maize and its wild ancestor

One of the greatest agricultural and evolutionary puzzles is the origin of maize–and part of the answer may lie in a plot of corn on the western edge of Madison, where a hybrid crop gives new life to ancient genetic material.

While many biologists argue that teosinte, a wild Mexican grass, is the progenitor of maize, others believe that the differences between teosinte and maize are too complex to have arisen through natural mutation or human selection. One of the most significant inconsistencies between the two plants is that teosinte kernels are locked in a hardened casing and have to be cracked like walnuts, while maize kernels are exposed on the surface of the ear.

However, a team led by a UW-Madison geneticist has demonstrated that a single gene, called tga1, controls kernel casing. And beyond implications for the study of maize evolution, the results are evidence that modest alterations in single genes can cause dramatic changes in the way traits are expressed, the team wrote in the August issue of the journal Nature.

“What really interests me is how traits evolve,” says John Doebley, the professor of genetics in the College of Agricultural and Life Sciences who led the study. “How did changes in genes cause the diversity of life to arise on earth? The corn and teosinte model is an excellent system to investigate this question.”

While Doebley has laboratory facilities on campus, he is equally at home in the field plots at the West Madison Agricultural Research Station where he raises second-generation hybrids of teosinte and maize. He studies the inheritance of different traits in the hybrids and uses genetic tools to identify the genes involved, applying highly advanced technology to an